1. Field of the Invention
The present invention relates generally to dewatering equipment and more particularly, to a system that semi-continuously filters both fibrous materials and particulate materials from slurries, producing a substantially dry filter cake. The system further deposits the cake in containers, and when required, returns the relatively clean filtrate to be reused.
2. Brief Description of Prior Art
Solid-liquid separation is a major unit operation that exists in almost every flow scheme related to the chemical process industries, ore beneficiation, pharmaceutics, food, or water and waste treatment. The lack of cost effective equipment to handle these major unit operations and the enormous pollution problems caused by fluid production systems has resulted in industries abandoning many thousands of refuse ponds. The coal industry has created several hundred coal refuse slurry ponds holding an estimated 2 to 3 billion tons of discarded fine coal particles. Each year an estimated 30 million more tons are discarded into these waste ponds. Most of these slurry ponds are abandoned, un-monitored, and pose an enormous environmental hazard.
Existing methods of slurry management by industry using slurry ponds, concrete pools or plastic lined pools for slurry storing or processing are not environmentally sound. Tighter governmental monitoring of slurry ponds has brought about the need for active solid-liquid separation devices that are both economical and environmental effective. Prior art systems have not been effective. Many such prior art systems are not automated or continuous, or semi-continuous. Such prior art systems typically use disposable filter or cloth. Other systems may also use elastomeric diaphragms which limit the chamber size. Others apply heat or chemicals or both which reduce the reliability and raise the cost of operation. Centrifuges and belt presses have not been the answer in most cases. Some inventions use compression chambers that separate with an upper part and lower part that require hundreds of thousands pounds of force to hold the two parts together. Although these work for low throughputs, the design limits their applications and the cost per gallon slurry processed is high. Some use stacked multiple chambers increasing the complexity and manufacturing costs while reducing the reliability. Vacuum disc filters have proved unreliable, have low throughput, and fail to produce “dry” solids that meet industry standards. Others have tried the vacuum-atmosphere technique, with and without membranes, which has not been effective in creating “dry” solids.
Dewatering equipment can be used to clean up these environmental liabilities. The dewatering equipment needed must be of reasonable cost, non-labor intensive, reliable, adaptable to different slurries, and able to handle high throughput. It must make the disposal of or reuse of the treated materials both economical and environmental effective.
As will be seen from the subsequent description, the preferred embodiments of the present invention overcome short comings of the prior art.